This invention relates generally to a compressor and more particularly to a variable-displacement wobble plate compressor suited for a coolant compressor for an air conditioner for an automobile.
A conventional variable-displacement wobble plate compressor as disclosed in U.S. Pat. No. 4,428,718 includes a swash plate which has a swash plate portion and a boss portion rotatably supporting a piston support wobble plate, with the boss portion being formed integrally with the swash plate portion. The swash plate is tiltably supported at its boss portion by a sole sleeve slidable along a drive shaft. Particularly, in this construction, the swash plate portion is deviated from the center or axis of tilting of the swash plate relative to the sleeve.
In the above conventional construction, as compared with a tilting moment of the swash plate plane due to an inertia couple produced by a reciprocal movement of each piston, a tilting moment of the swash plate plane due to a centrifugal force produced by the rotation of the swash plate portion and acting in an opposite direction is smaller. This results in a problem that the unbalanced tilting moment due to the inertia force remains.
The above unbalanced tilting moment due to the inertia force increases in proportion to the square of the rotation and the direction of this tilting moment is such that increases the tilting angle of the swash plate. Therefore, a problem arises in that, during a high-speed operation, it is difficult to effect the control in such a direction as to decrease the angle of the swash plate.
Further, since the swash plate portion is deviates from the axis of rotation of the swash plate relative to the sleeve as described above, its center of gravity deviates from the axis of rotation of the drive shaft, depending on the angle of tilt of the swash plate plane relative to the drive shaft, so that the resultant force of the centrifugal forces acting on the various regions of the swash plate portion will not become zero. This unbalanced centrifugal force and the above-mentioned unbalanced moment are transmitted to the exterior of the compressor to thereby cause vibrations.
Particularly, the above unbalanced inertia force varies in magnitude in accordance with the variation of the tilt angle of the swash plate effected during the displacement control of the compressor, and therefore even if a balance mass is fixed to the drive shaft, it has been impossible to always achieve a balance with respect to all the tilt angles of the swash plate.